The present invention relates generally to cold-exchange systems, and more particularly to Dewar flask cold exchange systems and vacuum separator apparatus for such systems.
Dewar flask cold exchange or cryogenic systems or cryostats have long been used to provide extremely low and substantially constant temperature. Systems of this type are frequently used to cool electronic detectors which use high purity semi-conductors, such as infrared, x-ray, or gamma ray detectors. Cooling the semi-conductors reduces the amount of "white noise" inherent in electronic components that reduces the accuracy of the electronic detector.
In Dewar flask cryogenic systems, a cold-exchange reservoir is contained within an outer vessel, defining a chamber therebetween. A vacuum is drawn in the chamber to reduce the thermal conductivity from the reservoir to the outside environment. The reservoir is filled with a cryogenic liquid, such as liquid nitrogen, which is permitted to evaporate as gaseous nitrogen, thereby reducing the temperature of the cold-exchange reservoir. The detector to be cooled is situated apart from the cold-exchange reservoir with some type of heat transfer connection between the detector and the reservoir of the flask.
In order to prevent contamination of the high-purity semi-conductor in the detector device, some form of vacuum separator has typically been used to isolate the detector from the vacuum within the Dewar flask, while maintaining the heat transfer relationship. Typical cryogenic systems of the prior art have used a stainless steel bellows in order to maintain the separation between the detector and the Dewar flask. One problem with the metallic bellows of the prior art is that the bellows provides an additional heat transfer path from the cold-exchange reservoir to the outside environment. Thus, the cryogenic liquid within the Dewar cold-exchange reservoir evaporates at a faster rate, reducing the time the system may be operational without cryogen re-fill.